Physicists are more like avant-garde composers, willing to bend traditional rules and brush the edge of acceptability in the search for solutions. Mathematicians are more like classical composers, typically working within a much tighter framework, reluctant to go to the next step until all previous ones have been established with due rigor. Each approach has its advantages as well as drawbacks; each provides a unique outlet for creative discovery. Like modern and classical music, it’s not that one approach is right and the other wrong – the methods one chooses to use are largely a matter of taste and training.

Superstring theory starts off by proposing a new answer to an old question: what are the smallest, indivisible constituents of matter? For many decades, the conventional answer has been that matter is composed of particles... that can be modeled as dots that are indivisible and that have no size and no internal structure. Conventional theory claims, and experiments confirm, that these particles combine in various ways to produce protons, neutrons, and a wide variety of atoms and molecules... Superstring theory tells a different story. ...it does claim that these particles are not dots. Instead... every particle is composed of a tiny filament of energy, some hundred billion billion times smaller than a single atomic nucleus, which is shaped like a string. And just as a violin string can vibrate in different patterns, each of which produces a different musical tone, the filaments of superstring theory can also vibrate in different patterns. But these vibrations... produce different particle properties. ...All species of particles are unified in superstring theory since each arises from a different vibrational pattern executed by the same underlying entity.

The Elegant Universe (1999)

The real question is whether all your pondering and analyses will convince you that life is worth living. That's what it all comes down to.

Well, a big question is how did the universe begin. And we, cannot answer that question. Some people think that the big bang is an explanation of how the universe began, its not. The big bang is a theory of how the universe evolved from a split second after whatever brought it into existence. And the reason why we’ve been unable to look right back at time zero, to figure out how it really began; is that conflict between Einstein’s ideas of gravity and the laws of quantum physics. So, string theory may be able to - it hasn’t yet; we’re working on it today - feverishly. It may be able to answer the question, how did the universe begin. And I don’t know how it’ll affect your everyday life, but to me, if we really had a sense of how the universe really began, I think that would, really, alert us to our place in the cosmos in a deep way.

In response to David Letterman's question, "What do we now know [about the universe] we didn’t know before?"

The Fabric of the Cosmos covers a wider field than The Elegant Universe and paints it with a broader brush. There is not much overlap between the two books. ...Neither is a prerequisite for reading the other. The new book is easier, and should preferably be read first. Readers who get stuck halfway through The Elegant Universe may find the new book more digestible.

Greene takes it for granted, and here the great majority of physicists agree with him, that the division of physics into separate theories for large and small objects is unacceptable. ...Greene believes that there is an urgent need to find a theory of quantum gravity that applies to large and small objects alike. ...As a conservative, I do not agree that a division of physics into separate theories for large and small is unacceptable. ...The essence of any theory of quantum gravity is that there exists a particle called the graviton... I looked at various possible ways of detecting gravitons and did not find a single one that worked. Because of the extreme weakness of the gravitational interaction, any putative detector of gravitons has to be extremely massive. If the detector has normal density, most of it is too far from the source of gravitons to be effective, and if it is compressed to a high density around the source it collapses into a black hole. There seems to be a conspiracy of nature to prevent the detector from working.